• 농촌계획
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• 제10권3호
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• pp.27-32
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• 2004

The purpose of this study is on identifying the restoration guidelines of supplementary village grove and villageside forest in case of Neunggil village in Jinan county of Korea. These forests were managed very well before industrialization by village residents in order to obtain fuels and organic fertilizers traditionally. But recently, these forests were abandoned by using natural gas, oil and chemical fertilizer. Therefore, species diversity of these forests was downward and traditional rural landscape was lost. Accordingly, this study suggested the restoration guidelines of these forests through restoring the relationship between man and nature. For this, vegetation map was made by quadrat method. And management guidelines of these forests were suggested by the analysis of vegetation map. Also, for the restoration of supplementary village grove, Miyawiki professor's method of Yokohama university through introducing potential natural vegetation was suggested.

• 한국소음진동공학회논문집
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• 제16권3호
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• pp.240-246
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• 2006

In the air-conditioner, refrigerant induced noise and vibration can be increased when the airflow rate is reduced in order to decrease the noise at the low mode. Through the test and analysis of this kind of noise, it can be verified that the main reasons of refrigerant induced noise are the velocity and flow Induced force of the refrigerant at the inlet of the evaporator, So, in order to reduce this velocity, quality at the evaporator inlet should be minimized. And, in order to reduce flow induced force of the refrigerant, sudden change of fluid flow must not be occurred. So, in this paper, we will review the characteristics of refrigerant cycle and find how the quality and flow induced force can be minimized.

• Advances in environmental research
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• 제5권2호
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• pp.79-94
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• 2016

In order to evaluate the contamination and health risk, levels of six hazardous elements i.e., Cr, Ni, Cu, As, Cd and Pb in soils of 12 different land-uses were measured. The average concentration of Cu, Cr, Ni, Pb, As and Cd in soils were 267, 239, 206, 195, 58 and 16 mg/kg, respectively. Levels of each metal exceeded the environmental action level for soils, which could pose significant risk to human. The metal concentrations were subsequently used to establish hazard indices (for adults and children) where the 5th and 95th percentile values were used to derive the hazard index through different exposure pathways (ingestion, dermal contact and inhalation). Considering the total exposure through each of the three pathways, the hazard index elucidates that there was a potency of non-cancer risk at most of the sites for both the adults and children. The findings of this study suggested that different land-use soils were severely contaminated with hazardous elements and attention is needed on the potential health risks to the exposed inhabitants.

• Wind and Structures
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• 제11권6호
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• pp.455-478
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• 2008

The present study aims to estimate the wind ventilation performance for pedestrian level domains from the air quality point of view. Three typical models of a dense urban area were considered and numerically simulated in order to examine the effects of the geometry of such models on wind flow characteristics, which in turn affect the air quality, within the pedestrian domain of a street canyon located within this area. The calculated flow fields were employed to estimate the exceedance probabilities within the study domain using a new approach: air exchange rate within the domain. The study has been applied to nine cities in Japan: Tokyo, Osaka, Sapporo, Niigata, Fukuoka, Nagoya, Sendai, Yokohama, and Kyoto, based on their mean wind velocity data. The results demonstrated that the exceedance probability analysis of the pedestrian wind environment could be a valuable tool during the design stage of inhabited areas for the evaluation of pollutant-removal efficiency by the applied wind. Also, the calculated probabilities demonstrated substantial dependence on both the geometry of building arrays and the wind conditions of the nine cities.

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1125-1138
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• 2006

The optimal design of the squeeze film damper (SFD) for rotor system has been studied in previous researches. However, these researches have not been considering jumping or nonlinear phenomena of a rotor system with SFD. This paper represents an optimization technique for linear and nonlinear response of a simple rotor system with SFDs by using a hybrid GA-SA algorithm which combined enhanced genetic algorithm (GA) with simulated annealing algorithm (SA). The damper design parameters are the radius, length and radial clearance of the damper. The objective function is to minimize the transmitted load between SFD and foundation at the operating and critical speeds of the rotor system with SFD which has linear and nonlinear unbalance responses. The numerical results show that the transmitted load of the SFD is greatly reduced in linear and nonlinear responses for the rotor system.

• Journal of Communications and Networks
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• 제17권4호
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• pp.419-427
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• 2015

There have been increases in the elderly population worldwide, and this has been accompanied by rapid growth in the health-care market, as there is an ongoing need to monitor the health of individuals. Wireless body area networks (WBANs) consist of wireless sensors attached on or inside the human body to monitor vital health-related problems, e.g., electrocardiograms (ECGs), electroencephalograms (EEGs), and electronystagmograms (ENGs). With WBANs, patients' vital signs are recorded by each sensor and sent to a coordinator. However, because of obstructions by the human body, sensors cannot always send the data to the coordinator, requiring them to transmit at higher power. Therefore, we need to consider the lifetime of the sensors given their required transmit power. In the IEEE 802.15.6 standard, the transmission topology functions as a one-hop star plus one topology. In order to obtain a high throughput, we reduce the transmit power of the sensors and maintain equity for all sensors. We propose the multiple-hop transmission for WBANs based on the IEEE 802.15.6 carrier-sense multiple-access with collision avoidance (CSMA/CA) protocol. We calculate the throughput and variance of the transmit power by performing simulations, and we discuss the results obtained using the proposed theorems.

• 한국대기환경학회지
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• 제21권3호
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• pp.285-293
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• 2005

This study was aimed at estimation of gas-particle partitioning of polychlorinated biphenyls (PCBs) in ambient air. The samples were collected at urban site in Japan from March 2002 to January 2003. The concentration of total PCBs (from 4 CB to 10 CB) and TEQ (Toxic equivalent) ranged from 62 to $247\;pg/m^3$ and from 2 to $14\;fgTEQ/m^3 $, respectively. The average contribution $(\%)$ of gas phase to total PCBs concentration was above $80\%$, which suggests that in the atmosphere PCBs predominantly existed in the gas phase. The weak correlations between total PCBs concentration and temperature was found. However this result was due to a typhoon during summer and raining during sampling period. The gas-particle partition coefficient (Kp) was obtained as a function of temperature. The partition ratio of gaseous and particulate phase PCBs can be estimated for an arbitrary temperature. The plot of gas/particle partition coefficient (log Kp) vs. sub-cooled liquid vapor pressure $(log\;P_L)$ had reasonable correlations for individual samples but the slope varied among the samples (coefficients of determination for log Kp versus log $P_L$ plot were> 0.76 $(p<0.0001)$, except for 3 samples). As a result, the variations in the slope among the sampling period may be due to change of temperature, raining during sampling period and wind in this study.

• Journal of electromagnetic engineering and science
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• 제2권2호
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• pp.117-123
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• 2002

This paper describes the design for the resistive FET mixer with low If for the 4-Ch DBF(Digital Beam Forming) receiver This DBF receiver based on the direct conversion method is generally suitable for high-speed wireless mobile communications. A radio frequency(RF), a local oscillator(LO) and an intermediate frequency(If) considered in this research are 2.09 GHz, 2.08 CHz and 10 MHz, respectively. This mixer is composed of band pass filter, a low pass filter and a DC bias circuit. Super low noise HJ FET of NE3210S01 is considered in design. The RE input power, LO input power and Vcs are used -10 dBm, 6 dBm and -0.4 V, respectively. In the 4-Ch resistive FET mixer, the measured If and harmonic components of 10 MHe, 20 MHz and 2.087 CHz are about -19.2 dBm, -66 dBm and -48 dBm, respectively The If output power observed at each channel of 10 MHz is about -19.2 dBm and it is higher 28.8 dBm than the maximum harmonic component of 2.087 CHz. Each If output spectrum of the 4-Ch is observed almost same value and it shows a good agreement with the prediction.

• 설비공학논문집
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• 제18권2호
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• pp.151-157
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• 2006

The present paper reports the method for evaluation of heat-transfer performance of finned tube heat exchangers in a low Reynolds number regime (Re = $160\~800$) and also reports the data of heat transfer and pressure loss taken from a finned tube heat exchanger with/without vortex generators (VGs) installed as a heat-transfer enhancement device. The evaluation is based on the modified single blow method conducted in a specially designed low Reynolds number duct. Three different test core geometries, i.e., fin only, fin-tube without VGs and that with VGs, are studied here. The data of heat transfer and pressure loss taken from the fin only geometry agree well with the empirical correlations, thus validating the present method as used for low Reynolds number regime. The data taken from the finned tube geometries with and without VGs are presented and compared to examine the effect of VGs in the low Reynolds number regime.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.3-3
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• 2002

Many studies on crystal growth mechanisms of the hen egg-white lysozyme protein crystals have mainly performed by optical microscopy and atomic force microscopy (AFM). As results, two types of growth mechanisms, which are a two-dimensional nucleation mechanism and a spiral growth mechanism, were identified. However, there was no direct evidence of grown-in screw dislocations at the spiral sites. We first observed the screw dislocations in tetragonal lysozyme crystals using synchrotron X-ray topography. In addition, to confirm the characteristics of dislocations, we have observed some elastic constants in lysozyme crystals in terms of the sound velocity measurement by pulse echo methods. Tetragonal hen egg-white lysozyme crystals were grown by the concentration gradient method. The crystals were grown in test tubes, with an inner diameter of 8 ㎜ and 80 ㎜ in length, held vertically. The test tubes were kept at 23C for 2 weeks. The maximum size of crystals were 3×3×4 ㎟. The high quality crystals were examined by Laue topography with a water filter using synchrotron radiation. Figure is a X-ray topograph. Several straight screw dislocations were observed. We also determined Burgers vector to be a [110] direction. The measurement of sound velocity was performed by the digital signal processing method. the crystals were placed in stainless steel vessel, which was filled with lysozyme solution used for crystal growth. We observed the longitudinal sound velocity along the [110] direction in the tetragonal is obtained to be 1817 ㎧. Therefore, Young modulus and shear modulus were evaluated to be 2.70 Gpa and 1.02 Gpa, respectively, if we assumed Poisson ratio is 0.33. These results will be discussed at the meeting.